AU2019231059B2 - Heartbeat rate calculation device and method - Google Patents
Heartbeat rate calculation device and method Download PDFInfo
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/316—Modalities, i.e. specific diagnostic methods
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/316—Modalities, i.e. specific diagnostic methods
- A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
- A61B5/346—Analysis of electrocardiograms
- A61B5/349—Detecting specific parameters of the electrocardiograph cycle
- A61B5/352—Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
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- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/024—Detecting, measuring or recording pulse rate or heart rate
- A61B5/0245—Detecting, measuring or recording pulse rate or heart rate by using sensing means generating electric signals, i.e. ECG signals
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/30—Input circuits therefor
- A61B5/304—Switching circuits
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- A—HUMAN NECESSITIES
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- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
- A61B5/316—Modalities, i.e. specific diagnostic methods
- A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
- A61B5/346—Analysis of electrocardiograms
- A61B5/349—Detecting specific parameters of the electrocardiograph cycle
- A61B5/364—Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
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Abstract
In the present invention, a first computation unit (102) determines the heart rate of a subject from a plurality of instant heart rates (heartbeat rates) by an averaging process with an IIR filter using a first coefficient. The first coefficient is a numeric value of less than 1 and is a fixed value. A second computation unit (103) determines the heart rate of the subject from the plurality of instant heart rates by an averaging process with the IIR filter using a second coefficient. The second coefficient is a numeric value of less than 1 and is a variable value. A switching unit (104) switches between the first computation unit (102) and the second computation unit (103) on the basis of the difference between the heart rate previously determined and the latest instant heart rate.
Description
Specification
Technical Field
[0001] The present invention relates to a heartbeat count calculation apparatus and method for calculating a heartbeat count such as a heart rate or a pulse rate and, particularly, to a heartbeat count calculation apparatus and method capable of stably calculating a heartbeat count even if instantaneous heartbeat counts include an abnormal value.
Background Art
[0002] Measurement of a heart rate fluctuation is useful to control the loading intensity of the cardiopulmonary function. In recent years, a wearable device that can measure an electrocardiogram by incorporating an electrode in clothing such as a shirt has been developed. Thus, in various scenes, a heart rate fluctuation is monitored and observed.
Related Art Literature Non-Patent Literature
[0003] Non-Patent Literature 1: C. Park et al., "An Ultra-Wearable, Wireless, Low Power ECG Monitoring System", Biomedical Circuits and Systems Conference, 2006. BioCAS 2006. IEEE.
[0004] However, a wearable heart rate measurement device may lead a heart rate detection error since noise is readily added to a measurement result (electrocardiographic waveform). As a result, instantaneous heart rates for respective beats obtained in time series from the measured electrocardiographic waveform include an abnormal value. To prevent calculation of such abnormal value, it is important to appropriately average the instantaneous heart rates obtained from the measured electrocardiographic waveform.
[0005] As an averaging technique, for example, non- patent literature 1 describes a technique in which when calculating a heart rate from instantaneous heart rates obtained from an electrocardiographic waveform, the moving average of input data points is obtained until predetermined data points as moving average targets are input. However, processing when time series data of the instantaneous heart rates include an abnormal value is not mentioned.
[0006] Since noise is readily added to an electrocardiographic waveform obtained using a wearable device to lead a heart rate detection error, instantaneous heart rates include an abnormal value. Therefore, to monitor the transition of the heart rate, it is important to obtain an appropriately averaged heart rate (instantaneous heart rate).
[0007] The present invention has been made in consideration of the above problems. Aspects of the present disclosure calculate a heart rate appropriately even if instantaneous heartbeat counts concerning the heartbeat count of the heart, such as instantaneous heart rates, include an abnormal value.
Summary
[0007a] It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages.
[0007b] According to an aspect of the present invention, there is provided a heartbeat count calculation apparatus comprising: an extraction unit configured to extract a plurality of instantaneous heartbeat counts concerning a heartbeat count of a heart in time series from biometric information; a first calculation unit configured to calculate the heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with afirst infinite impulse response (1IR) filter; a second calculation unit configured to calculate the heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with a second IIR filter having a faster response than the first IIRfilter; and a switching unit configured to switch between the first calculation unit and the second calculation unit based on a difference between the heartbeat count calculated by one of the first calculation unit and the second calculation unit and a latest instantaneous heartbeat count extracted by the extraction unit; wherein the first IIR filter uses afirst coefficient of a fixed value smaller than 1; wherein the second IIR filter uses a second coefficient of a variable value smaller than 1; wherein in afirst state, in which the difference between the latest instantaneous heartbeat count and the heartbeat count calculated by the first calculation unit is not smaller than a set first constant continues during a set first heartbeat count, the switching unit switches from the first calculation unit to the second calculation unit, and wherein in a second state, in which the difference between the latest instantaneous heartbeat count and the heartbeat count calculated by the second calculation unit is not larger than a set second constant continues during a set second heartbeat count and a third state in which the second coefficient is equal to the first coefficient, the switching unit switches from the second calculation unit to the first calculation unit.
[0007c] According to another aspect of the present invention, there is provided a heartbeat count calculation method comprising: a first step of extracting a plurality of instantaneous heartbeat counts in time series from biometric information; a second step of obtaining a heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with afirst infinite impulse response (1IR) filter; a third step of obtaining a heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with a second IIR filter having a faster response than the first IIR filter; and a fourth step of switching between the second step and the third step based on a difference between an extracted latest instantaneous heartbeat count and the heartbeat count precedingly obtained in one of the second step and the third step; wherein the first IIR filter uses afirst coefficient of a fixed value smaller than 1; wherein the second IIR filter uses a second coefficient of a variable value smaller than 1; wherein in a first state, in which the difference between the latest instantaneous heartbeat count and the heartbeat count obtained in the second step is not smaller than a setfirst constant continues during a set first heartbeat count, switching the second step to the third step, and wherein in a second state, in which the difference between the latest instantaneous heartbeat count and the heartbeat count obtained in the third step is not larger than a set second constant continues during a set second heartbeat count and a third state in which the second coefficient is equal to the first coefficient, switching the third step to the second step.
[0008] According to the present invention, there is provided a heartbeat count calculation apparatus comprising an extraction unit configured to extract a plurality of instantaneous heartbeat counts concerning a heartbeat count of a heart in time series from biometric information, a first calculation unit configured to obtain the heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with an IIR filter using a first coefficient of a fixed value smaller than 1, a second calculation unit configured to obtain the heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with an IIR filter using a second coefficient of a variable value smaller than 1, and a switching unit configured to switch between the first calculation unit and the second calculation unit based on a difference between the heartbeat count obtained by one of the first calculation unit and the second calculation unit and a latest instantaneous heartbeat count extracted by the extraction unit.
[0009] According to the present invention, there is also provided a heartbeat count calculation method comprising a first step of extracting a plurality of instantaneous heartbeat counts in time series from an electrocardiographic waveform of a living body, a second step of obtaining a heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with an IIR filter using a first coefficient of a fixed value smaller than 1, a third step of obtaining a heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with an IIR filter using a second coefficient of a variable value smaller than 1, and a fourth step of switching between the second step and the third step based on a difference between an extracted latest instantaneous heartbeat count and the heartbeat count precedingly obtained in one of the second step and the third step.
[0010] As described above, according to the present invention, it is possible to obtain a great effect of calculating a heartbeat count appropriately even if instantaneous heartbeat counts include an abnormal value.
Brief Description of Drawings
[0011] Fig. 1 is a block diagram showing the arrangement of a heartbeat count calculation apparatus according to an embodiment of the present invention;
Fig. 2 is a flowchart for explaining a
heartbeat count calculation method according to the
embodiment of the present invention;
Fig. 3 is a flowchart for explaining, in more
detail, the heartbeat count calculation method according
to the embodiment of the present invention;
Fig. 4 is a timing chart showing a change in
heartbeat count calculated in a heartbeat count
calculation mode (first mode) by a first calculation
unit 102 by setting an averaging coefficient a (first
coefficient) to 0.1;
Fig. 5 is a timing chart showing a change in
heartbeat count calculated in the heartbeat count
calculation mode (first mode) by the first calculation
unit 102 by setting the averaging coefficient a (first
coefficient) to 0.1 and a change in heartbeat count
calculated in a heartbeat count calculation mode (second
mode) by a second calculation unit 103 by setting an
averaging coefficient a (second coefficient) to a = 0.5
- 0.4 x N/20;
Fig. 6 is a timing chart showing a change in
heartbeat count of a human when suddenly performing an
exercise such as pedaling with full force from a rest
state;
Fig. 7 is a block diagram showing the
arrangement of another heartbeat count calculation apparatus 100a according to the embodiment of the present invention;
Fig. 8A is an explanatory timing chart showing
an example of determination of an abnormal period;
Fig. 8B is an explanatory timing chart showing
an example of determination of an abnormal period;
Fig. 8C is an explanatory timing chart showing
an example of determination of an abnormal period;
Fig. 8D is an explanatory timing chart showing
an example of determination of an abnormal period;
Fig. 8E is an explanatory timing chart showing
an example of determination of an abnormal period; and
Fig. 9 is a block diagram showing the hardware
arrangement of the heartbeat count calculation apparatus
according to the present invention.
Best Mode for Carrying Out the Invention
[0012] A heartbeat count calculation apparatus 100
according to an embodiment of the present invention will
be described below with reference to Fig. 1. The
heartbeat count calculation apparatus 100 includes an
extraction unit 101, a first calculation unit 102, a
second calculation unit 103, and a switching unit 104.
[0013] The extraction unit 101 extracts a plurality
of instantaneous heartbeat counts concerning the
heartbeat count of the heart in time series from
biometric information obtained from a target living body
(subject). The biometric information is, for example, the electrocardiographic waveform of the subject obtained by measurement using an electrocardiograph 121, and the heartbeat count is a heart rate. As is well known, an instantaneous heart rate is obtained based on the R-R interval of the electrocardiographic waveform.
If the R-R interval is 2 sec, an instantaneous heart
rate is 30 times/min by calculating 60 sec/2. A heart
rate will be exemplified as a heartbeat count.
[0014] The first calculation unit 102 obtains the
heart rate (heartbeat count) of the subject from a
plurality of instantaneous heart rates (instantaneous
heartbeat counts) by averaging processing with an IIR
(Infinite Impulse Response) filter using the first
coefficient. Note that the first coefficient is a
numerical value smaller than 1, and is a fixed value.
The first calculation unit 102 updates the heart rate by
obtaining the heart rates in time series by, for
example, multiplying an instantaneous heart rate at a
given time by the first coefficient, and adding, to the
thus obtained value, a value obtained by multiplying an
instantaneous heart rate at an immediately preceding
time by a value obtained by subtracting the first
coefficient from 1 [heart rate at current time =
(instantaneous heart rate x first coefficient) + {heart
rate at immediately preceding time x (1 - first
coefficient)}].
[0015] The second calculation unit 103 obtains the heart rate of the subject from the plurality of instantaneous heart rates by averaging processing with an IIR filter using the second coefficient. The second coefficient is a numerical value smaller than 1 and is a variable value. The second calculation unit 103 updates the heart rate by obtaining the heart rates in time series by, for example, adding, to a value obtained by multiplying the instantaneous heart rate by the second coefficient, a value obtained by multiplying the heart rate at the immediately preceding time by a value obtained by subtracting the second coefficient from 1.
The second calculation unit 103 includes a processing
unit 103a that starts the second coefficient with a
value larger than the first coefficient and makes the
second coefficient closer to the first coefficient for
each beat. The calculation unit 103 uses the second
coefficient having undergone coefficient processing by
the processing unit 103a.
[0016] The switching unit 104 switches between the
first calculation unit 102 and the second calculation
unit 103 based on the difference between the precedingly
obtained heart rate and the latest instantaneous heart
rate. The switching unit 104 switches, from one of the
first calculation unit 102 and the second calculation
unit 103 to the other, a processing unit that is to
obtain a heart rate output from the heartbeat count
calculation apparatus. The switching unit 104 determines, based on the difference between the precedingly calculated heart rate and the latest instantaneous heart rate, whether to leave one of the calculation units that has calculated the heart rate last time as a processing unit to perform processing for calculating a heart rate using the latest instantaneous heart rate, or switch from the calculation unit to the other, and, when it has determined to switch the processing unit, the switching unit 104 switches the processing unit. The heartbeat count calculation apparatus outputs the heart rate calculated by the first calculation unit 102 or the second calculation unit 103 switched by the switching unit 104.
[0017] The switching unit 104 switches from the first
calculation unit 102 to the second calculation unit 103
in, for example, the first state in which a state in
which the difference between the latest instantaneous
heart rate and the heart rate calculated by the first
calculation unit 102 is equal to or larger than the set
first constant continues during the set first heart
count.
[0018] Furthermore, the switching unit 104 switches
from the second calculation unit 103 to the first
calculation unit 102 in, for example, the second state
in which a state in which the difference between the
latest instantaneous heart rate and the heart rate
calculated by the second calculation unit 103 is equal to or smaller than the set second constant continues during the set second heartbeat count or the third state in which the second coefficient is equal to the first coefficient.
[0019] For example, if the first calculation unit 102
calculates the heart rate last time and the difference
between this heart rate and the instantaneous heart rate
extracted by the extraction unit 101 this time is in the
first state, the switching unit 104 performs switching
processing. In this case, the second calculation unit
103 calculates the heart rate this time. Alternatively,
for example, if the second calculation unit 103
calculates the heart rate last time, and the difference
between this heart rate and the instantaneous heart rate
extracted by the extraction unit 101 this time is in the
second or third state, the switching unit 104 performs
switching processing. In this case, the first
calculation unit 102 calculates the heart rate this
time.
[0020] The heartbeat count calculation apparatus 100
according to the embodiment includes an update stopping
unit 105 in addition to the above-described components.
The update stopping unit 105 stops update of the heart
rate when the difference between the latest
instantaneous heart rate and the heart rate calculated
by the first calculation unit 102 exceeds a set
reference value, and limits the update value of the heart rate when the difference between the heart rate calculated at the current time by the first calculation unit 102 and that calculated at the immediately preceding time by the first calculation unit 102 exceeds the set reference value.
[0021] Next, an example (heartbeat count calculation
method) of the operation of the heartbeat count
calculation apparatus 100 according to the embodiment
will be described with reference to Fig. 2.
[0022] In step S101, the extraction unit 101 extracts
a plurality of instantaneous heart rates in time series
from biometric information obtained from a subject. The
biometric information is, for example, the
electrocardiographic waveform of the subject obtained by
measurement using the electrocardiograph 121. In step
S102, based on the difference between the latest
instantaneous heart rate extracted in step S101 and the
heart rate obtained last time, it is determined whether
to perform switching processing (fourth step). If it is
determined not to perform switching processing (NO in
step S102), a heart rate is obtained, in step S103, by
the same calculation processing as that performed last
time. On the other hand, if it is determined to perform
switching processing (YES in step S102), the switching
unit 104 switches the calculation processing in step
S104, and calculates a heart rate by calculation
processing switched in step S105. In step S106, the heartbeat count calculation apparatus 100 determines whether an end instruction has been input. If no end instruction has been input (NO in step S106), the process returns to step S101 to continue the processing.
[0023] For example, if the first calculation unit 102
calculates the heart rate last time (second step), and
the difference between this heart rate and the latest
instantaneous heart rate is in the first state, the
switching unit 104 determines, in step S102, to perform
switching processing, switches, in step S104, from the
first calculation unit 102 to the second calculation
unit 103, and calculates, in step S105, the heart rate
from the latest instantaneous heart rate by the second
calculation unit 103 (third step).
[0024] Alternatively, for example, if the second
calculation unit 103 calculates the heart rate last time
(third step), and the difference between this heart rate
and the latest instantaneous heart rate is in the second
or third state, the switching unit 104 determines, in
step S102, to perform switching processing, switches, in
step S104, from the second calculation unit 103 to the
first calculation unit 102, and calculates, in step
S105, the heart rate from the latest instantaneous heart
rate by the first calculation unit 102 (second step).
[0025] Note that in the heart rate calculation
processing by the second calculation unit 103, the
second coefficient starts with a value larger than the first coefficient, and is made closer to the first coefficient for each beat. This second coefficient processing is performed by the processing unit 103a.
Although not shown in Fig. 2, when the difference
between the latest instantaneous heart rate and the
heart rate calculated by the first calculation unit 102
exceeds the set reference value, update of the heart
rate can be stopped, and when the difference between the
heart rate calculated at the immediately preceding time
and that calculated at the current time exceeds the set
reference value, the update value of the heart rate can
be limited (fifth step).
[0026] [Example]
A more detailed description will be provided
using an example. Heart rate calculation processing by
a first calculation unit 102 will be referred to as the
first mode hereinafter, and heart rate calculation
processing by a second calculation unit 103 will be
referred to as the second mode hereinafter.
[0027] In both the first and second modes, as
averaging processing with an IIR filter for obtaining
the heart rate of a subject from a plurality of
instantaneous heart rates, a heart rate HR[n] is
calculated by "HR[n] = (1 - a) x HR[n-1] + a x IHR[n]"
using the averaging coefficient a for instantaneous
heart rates IHR[n] as n time-series data.
[0028] The averaging coefficient a takes a value of 0
< a < 1. As this value is smaller, a smoothing effect
of suppressing a fine fluctuation in the heart rate
HR[n] is higher while a delay when following a rough
change is larger.
[0029] In the first mode, the averaging coefficient a
is a fixed value (first coefficient). In the second
mode, the averaging coefficient a is a variable value
(second coefficient).
[0030] A heart rate calculation procedure according
to the example under the above-described conditions will
be described with reference to Fig. 3. Fig. 3 shows one
cycle of a procedure of calculating a heart rate from
instantaneous heart rates. Note that AHRi represents
the absolute value of a value obtained by subtracting,
from a heart rate, the latest instantaneous heart rate
when the heart rate is obtained. Furthermore, AHR
represents a value obtained by subtracting, from the
heart rate calculated at the current time, a heart rate
calculated at the immediately preceding time.
[0031] In step S201, it is determined whether the
current mode is the second mode. If the current mode is
the second mode, it is determined in step S202 whether
AHRi is equal to or smaller than 20 (second constant).
If AHRi is equal to or smaller than 20, 1 is added to a
counted number C2 (second heartbeat count) in step S203.
In step S204, it is determined whether the counted
number C2 is equal to 5. If the counted number C2 is equal to 5, in step S205 the second mode is switched to the first mode and the counted number C2 is set to 0.
On the other hand, if AHRi exceeds 20, the counted
number C2 is set to 0 in step S206.
[0032] If it is determined in step S201 that the
current mode is not the second mode, it is determined in
step S207 whether AHRi is equal to or larger than 40
(first constant). If AHRi is equal to or larger than
40, 1 is added to a counted number Cl (first heartbeat
count) in step S208. It is then determined in step S209
whether the counted number Cl is equal to 8. If the
counted number Cl is equal to 8, in step S210 the first
mode is switched to the second mode and the counted
number Cl is set to 0. On the other hand, if AHRi is
smaller than 40, the counted number Cl is set to 0 in
step S211.
[0033] In step S212, it is determined whether the
current mode is the second mode. If the current mode is
the second mode, it is determined in step S213 whether a
counted number C3 is equal to 20. If the counted number
C3 is equal to 20, in step S214 the second mode is
switched to the first mode and the counted number C3 is
set to 0. If the current mode is the first mode, it is
determined in step S215 whether AHRi is equal to or
larger than 40. If AHRi is smaller than 40, calculation
is performed in the first mode in step S216, and it is
determined in step S217 whether AHR is larger than 2 bpm. If AHR is larger than 2 bpm, HR[n] = HR[n-1] + 2 is set in step S218 as a heart rate update limitation.
If AHR is equal to or smaller than 2 bpm, it is
determined in step S219 whether AHR is smaller than -2
bpm. If AHR is smaller than -2 bpm, HR[n] = HR[n-1] - 2
is set in step S220 as a heart rate update limitation.
[0034] If it is determined in step S213 that the
counted number C3 is not equal to 20, in step S221
calculation is performed in the second mode and 1 is
added to the counted number C3, thereby ending the
processing of one cycle.
[0035] If it is determined in step S212 that the
current mode is not the second mode (the current mode is
the first mode), the process shifts to step S215.
[0036] In the above-described processing, in the
first mode, the averaging coefficient a is set to, for
example, 0.1. Under this condition, as shown in Fig. 4,
the heart rate HR[n] is moderately smoothed while a
delay for a change is allowable.
[0037] In the second mode, the averaging coefficient
a is given by, for example, "a = 0.5 - 0.4 x N/20 (N: a
beat count after shifting to the second mode). That is,
in the second mode, the averaging coefficient a starts
with 0.5, is decreased by 0.02 for each beat, and
returns to a value of 0.1 in the first mode at the 20th
beat. By temporarily making the averaging coefficient a
in the second mode large, the value of the instantaneous heart rate is strongly reflected, thereby obtaining an effect of accelerating convergence of the value of the heart rate.
[00381 If the initial instantaneous heart rate is an
abnormal value at the start of calculation of the heart
rate, it takes time for the heart rate to approach a
correct value in the first mode. However, if the second
mode is set in this status, the heart rate quickly
converges to the correct value, as shown in Fig. 5.
[00391 When an instantaneous heart rate largely
deviated from the heart rate continues, for example,
when an instantaneous heart rate deviated from the heart
rate by 40 bpm or more is successively obtained eight
times, the instantaneous heart rate at this time is
considered to be higher in reliability than the heart
rate before this time. Therefore, it is desired to
discard the heart rate before this time, and calculate a
heart rate based on the instantaneous heart rate at this
time. To do this, under the above condition, the mode
shifts to the second mode.
[0040] After the averaging coefficient a returns to a
value of 0.1 in the first mode, it is appropriate to set
the first mode in which the averaging coefficient a =
0.1 is maintained. Furthermore, if it is considered
that the difference between the heart rate and the
instantaneous heart rate has converged, even when, for
example, instantaneous heart rate deviated from the heart rate by 20 bpm or less is successively obtained five times, the mode shifts to the first mode, thereby making it possible to improve the smoothness of the heart rate.
[0041] Note that when, for example, suddenly
performing an exercise such as pedaling with full force
from a rest state, the heart rate of a human increases
at a rate of about 2 bpm/beat at most. Fig. 6 shows
this state. Conversely, it is hardly considered that
the heart rate increases at a rate exceeding 2 bpm/beat.
Therefore, if the change amount of the heart rate is
provided with an upper limit of 2 bpm/beat, it is
possible to prevent the obtained heart rate from being
an abnormal value.
[0042] As processing at each time when the
instantaneous heart rate is largely deviated from the
heart rate, for example, if the difference between the
instantaneous heart rate and the heart rate is equal to
or larger than 40 bpm, it is appropriate to consider the
instantaneous heart rate as an abnormal value, and this
value is discarded not to update the heart rate.
However, this corresponds to the first mode, and the
same does not apply to the second mode as a period for
recovering the state from the abnormal state.
[0043] Another heartbeat count calculation apparatus
100a according to the embodiment of the present
invention will be described next with reference to Fig.
7. The heartbeat count calculation apparatus 100a
includes an extraction unit 101, a first calculation
unit 102, a second calculation unit 103, and a switching
unit 104. These components are the same as those of the
above-described heartbeat count calculation apparatus
100.
[0044] The heartbeat count calculation apparatus 100a
includes an output control unit 106. The output control
unit 106 determines, as an abnormal period, a period
during which the second calculation unit 103 calculates
a heart rate, a period during which the difference
between the latest instantaneous heart rate and a heart
rate calculated by the first calculation unit 102
exceeds a reference value, or a period during which the
calculated heart rate falls within a set abnormal range,
and stops output of the heart rate during the abnormal
period. If, for example, the difference between the
instantaneous heart rate and the heart rate is equal to
or larger than 40 bpm, the calculated heart rate may
include an abnormal value or its influence.
Alternatively, the calculated heart rate may extremely
be deviated from an ordinary value to become an abnormal
value (falls within the set abnormal range) such as 0.
In this case, an abnormal period is determined to stop
output of the calculated heart rate.
[0045] Furthermore, the output control unit 106 can
be configured to determine, as the second abnormal period, a period until an abnormal period is determined again within a determination period set after the abnormal period, and stop output of the heart rate during the second abnormal period. For example, if an abnormal period is determined again within 30 sec after an abnormal period is determined, a period from the last determination of the abnormal period to this determination of the abnormal period is set as the second abnormal period, and output of the heart rate is stopped during the second abnormal period.
[0046] If the heart rate obtained during the abnormal
period falls within an allowable range set with respect
to the heart rate obtained during a period other than
the abnormal period, the output control unit 106 outputs
the heart rate (heartbeat count). Even during the
abnormal period, the difference between the obtained
heart rate and the heart rate obtained during the period
other than the abnormal period falls within, for
example, a range of ± 10 bpm, the obtained heart rate is
adopted as an output value.
[0047] A heartbeat count calculation method by the
heartbeat count calculation apparatus 100a can include
the following steps in addition to the steps described
with reference to Fig. 2. It is possible to set, as an
abnormal period, a period during which the second
calculation unit 103 (second step) calculates a heart
rate, a period during which the difference between the latest instantaneous heart rate and the heart rate calculated by the first calculation unit 102 (first step) exceeds the reference value, or a period during which the calculated heart rate falls within the set abnormal range, and stop output of the heart rate during the abnormal period (sixth step). If the heart rate obtained during the abnormal period falls within the allowable range set with respect to the heart rate obtained during the period other than the abnormal period, it is possible to output the heart rate
(heartbeat count) (seventh step). Furthermore, it is
possible to determine, as the second abnormal period, a
period until an abnormal period is determined again
within a determination period set after the abnormal
period, and stop output of the heart rate during the
second abnormal period (eighth step).
[0048] Examples of determination of the abnormal
period will be described below with reference to Figs.
8A, 8B, 8C, 8D, and 8E. Referring to Figs. 8A, 8B, 8C,
8D, and 8E, obtained heart rates are represented by open
circles.
[0049] In Fig. 8A, a result of determining whether
the obtained heart rate is a normal value or an abnormal
value is indicated by solid lines. If the heart rate is
a normal value, 0 is determined, and if the heart rate
is an abnormal value, 1 is determined. Time at which 1
is determined falls within an abnormal period, and thus the heart rate is not output.
[00501 In Fig. 8B, when an abnormal period is
determined again within 30 sec after an abnormal period
is determined, a result of determining, as an abnormal
value (a value of 1), an entire period from the last
determination of the abnormal period to this
determination of the abnormal period is indicated by
dotted lines. The period indicated by the dotted lines
during which a value of 1 is determined is set as the
second abnormal period for a heart rate acquisition
period, and the obtained heart rate is not output during
this period, as shown in Fig. 8C.
[0051] In Fig. 8D, a range of ±10 from each heart
rate value except for the heart rates obtained during
the above-described second abnormal period is indicated
by solid lines. Since not all the heart rates during
the second abnormal period are abnormal, the heart rate
within this range can be output, as shown in Fig. 8E.
[0052] In the above description, the
electrocardiographic waveform of a living body is used
as biometric information and a heart rate is used as a
heartbeat count. However, the present invention is not
limited to this. Information concerning a pulse can be
used as biometric information and a pulse rate can be
used as a heartbeat count. For example, a pulse
waveform is obtained in time series as biometric
information by irradiating the skin with light and measuring reflected light. Since the light absorption amount of blood changes depending on the pulse to change the reflected light intensity, it is possible to measure the pulse rate from the change in reflection intensity.
By forming, for example, an arrangement in which a
semiconductor light emitting element is used as a light
source and a photodiode measures reflected light, a
measurement apparatus can be downsized, thereby
obtaining a wristband type sensor. Such downsizing
makes it possible to very easily use the measurement
apparatus by mounting it on a subject.
[00531 Furthermore, for example, it is possible to
use, as a heartbeat count, a pulse rate obtained by
measuring a change in color of the skin surface of the
face or the like. Since the amount of light obtained
when the skin is irradiated with sunlight or
illumination light and reflects the light changes
depending on a pulse, a pulse rate can be measured using
a result of capturing the change by a camera or the
like. In this case, it is possible to obtain an
advantage that it is possible to measure a pulse rate in
a place away from the subject without mounting anything
on the subject.
[0054] Note that the heartbeat count calculation
apparatus according to the above-described embodiment is
a mobile computer apparatus including a CPU (Central
Processing Unit) 301, a main storage device 302, an external storage device 303, and a network connection device 304, as shown in Fig. 9. Each of the above described functions is implemented when the CPU 301 operates by a program loaded into the main storage device 302. Note that the network connection device 304 is connected to a network 305. The respective functions can also be distributed to a plurality of computer apparatuses.
[00551 The heartbeat count calculation apparatus
according to the above-described embodiment can be
formed by a PLD (Programmable Logic Device) such as an
FPGA (Field-Programmable Gate Array). For example, the
storage unit, the extraction unit, the first calculation
unit, the second calculation unit, and the switching
unit are provided as circuits in the logic elements of
an FPGA, the FPGA can be made to function as the
heartbeat count calculation apparatus. Each of the
storage unit, the extraction unit, the first calculation
unit, the second calculation unit, and the switching
unit is written in the FPGA by connecting a
predetermined writing device.
[00561 As described above, according to the present
invention, the first calculation unit that calculates a
heartbeat count from a plurality of instantaneous
heartbeat counts by averaging processing with an IIR
filter using the first coefficient of a fixed value
smaller than 1 and the second calculation unit that calculates the heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with an IIR filter using the second coefficient of a variable value smaller than 1 are switched based on the difference between the precedingly calculated heartbeat count and the latest instantaneous heartbeat count. As a result, according to the present invention, even if the instantaneous heartbeat counts include an abnormal value, it is possible to calculate a heartbeat count appropriately.
[0057] Note that the present invention is not limited
to the above-described embodiment, and it is obvious
that many modifications and combinations can be made by
a person with normal knowledge in the field within the
technical scope of the present invention.
Explanation of the Reference Numerals and Signs
[0058] 100...heartbeat count calculation apparatus,
101...extraction unit, 102...first calculation unit,
103...second calculation unit, 104...switching unit,
105...update stopping unit, 106...output control unit,
121...electrocardiograph
Claims (14)
1. A heartbeat count calculation apparatus comprising: an extraction unit configured to extract a plurality of instantaneous heartbeat counts concerning a heartbeat count of a heart in time series from biometric information; a first calculation unit configured to calculate the heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with a first infinite impulse response (1IR) filter; a second calculation unit configured to calculate the heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with a second IR filter having a faster response than the first IIR filter; and a switching unit configured to switch between the first calculation unit and the second calculation unit based on a difference between the heartbeat count calculated by one of the first calculation unit and the second calculation unit and a latest instantaneous heartbeat count extracted by the extraction unit; wherein the first IIR filter uses afirst coefficient of a fixed value smaller than 1; wherein the second IR filter uses a second coefficient of a variable value smaller than 1; wherein in a first state, in which the difference between the latest instantaneous heartbeat count and the heartbeat count calculated by the first calculation unit is not smaller than a set first constant continues during a set first heartbeat count, the switching unit switches from thefirst calculation unit to the second calculation unit, and wherein in a second state, in which the difference between the latest instantaneous heartbeat count and the heartbeat count calculated by the second calculation unit is not larger than a set second constant continues during a set second heartbeat count and a third state in which the second coefficient is equal to the first coefficient, the switching unit switches from the second calculation unit to the first calculation unit.
2. The heartbeat count calculation apparatus according to claim 1, wherein the second calculation unit includes a coefficient processing unit configured to start the second coefficient with a value larger than the first coefficient and make the second coefficient closer to the first coefficient for each beat.
3. The heartbeat count calculation apparatus according to any one of claims 1 to 2, further comprising an update stopping unit configured to stop update of the heartbeat count when the difference between the latest instantaneous heartbeat count and the heartbeat count calculated by the first calculation unit exceeds a set reference value, and to limit an update value of the heartbeat count when a difference between the heartbeat count calculated at an immediately preceding time by the first calculation unit and the heartbeat count calculated at a current time by the first calculation unit exceeds the set reference value.
4. The heartbeat count calculation apparatus according to any one of claims I to 3, further comprising an output control unit configured to determine, as an abnormal period, one of a period during which the second calculation unit calculates the heartbeat count, a period during which the difference between the latest instantaneous heartbeat count and the heartbeat count calculated by the first calculation unit exceeds the set reference value, and a period during which the calculated heartbeat count falls within a set abnormal range, and stop output of the heartbeat count during the abnormal period.
5. The heartbeat count calculation apparatus according to claim 4, wherein, if the heartbeat count obtained during the abnormal period falls within an allowable range set with respect to the heartbeat count obtained during a period other than the abnormal period, the output control unit outputs the heartbeat count.
6. The heartbeat count calculation apparatus according to any one of claims I to 5, wherein the biometric information is an electrocardiographic waveform of a living body, and the heartbeat count is a heart rate.
7. The heartbeat count calculation apparatus according to any one of claims I to 5, wherein the biometric information is information concerning a pulse, and the heartbeat count is a pulse rate.
8. A heartbeat count calculation method comprising: a first step of extracting a plurality of instantaneous heartbeat counts in time series from biometric information; a second step of obtaining a heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with a first infinite impulse response (IIR) filter; a third step of obtaining a heartbeat count from the plurality of instantaneous heartbeat counts by averaging processing with a second IIR filter having a faster response than the first
IIR filter; and a fourth step of switching between the second step and the third step based on a difference between an extracted latest instantaneous heartbeat count and the heartbeat count precedingly obtained in one of the second step and the third step; wherein the first IIR filter uses afirst coefficient of a fixed value smaller than 1; wherein the second IIR filter uses a second coefficient of a variable value smaller than 1; wherein in a first state, in which the difference between the latest instantaneous heartbeat count and the heartbeat count obtained in the second step is not smaller than a setfirst constant continues during a set first heartbeat count, switching the second step to the third step, and wherein in a second state, in which the difference between the latest instantaneous heartbeat count and the heartbeat count obtained in the third step is not larger than a set second constant continues during a set second heartbeat count and a third state in which the second coefficient is equal to the first coefficient, switching the third step to the second step.
9. The heartbeat count calculation method according to claim 8, wherein in the third step, the second coefficient starts with a value larger than thefirst coefficient, and is made closer to the first coefficient for each beat.
10. The heartbeat count calculation method according to any one of claims 8 to 9, further comprising a fifth step of stopping update of the heartbeat count when the difference between the latest instantaneous heartbeat count and the heartbeat count obtained in the second step exceeds a set reference value, and limiting an update value of the heartbeat count when a difference between the heartbeat count calculated at an immediately preceding time in the second step and the heartbeat count calculated at a current time in the second step exceeds the set reference value.
11. The heartbeat count calculation method according to any one of claims 8 to 10, further comprising a sixth step of determining, as an abnormal period, one of a period during which the heartbeat count is obtained in the third step, a period during which the difference between the latest instantaneous heartbeat count and the heartbeat count obtained in the second step exceeds the set reference value, and a period during which the obtained heartbeat count falls within a set abnormal range, and stopping output of the heartbeat count during the abnormal period.
12. The heartbeat count calculation method according to claim 11, further comprising a seventh step of outputting the heartbeat count when the heartbeat count obtained during the abnormal period falls within an allowable range set with respect to the heartbeat count obtained during a period other than the abnormal period.
13. The heartbeat count calculation method according to any one of claims 8 to 12, wherein the biometric information is the electrocardiographic waveform of a living body, and the heartbeat count is a heart rate.
14. The heartbeat count calculation method according to any one of claims 8 to 12, wherein the biometric information is information concerning a pulse, and the heartbeat count is a pulse rate.
Nippon Telegraph and Telephone Corporation
Patent Attorneys for the Applicant/Nominated Person
SPRUSON&FERGUSON
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| US7534212B2 (en) * | 2004-03-08 | 2009-05-19 | Nellcor Puritan Bennett Llc | Pulse oximeter with alternate heart-rate determination |
| JP2005269550A (en) * | 2004-03-22 | 2005-09-29 | Matsushita Electric Ind Co Ltd | Device and method for suppressing peak power |
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| TW201121501A (en) * | 2009-12-29 | 2011-07-01 | V Tac Technology Co Ltd | Examination method of exercise heart rate. |
| US20120157791A1 (en) * | 2010-12-16 | 2012-06-21 | General Electric Company | Adaptive time domain filtering for improved blood pressure estimation |
| JP5605269B2 (en) * | 2011-02-28 | 2014-10-15 | セイコーエプソン株式会社 | Beat detector |
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| US9770176B2 (en) * | 2011-09-16 | 2017-09-26 | Koninklijke Philips N.V. | Device and method for estimating the heart rate during motion |
| CN105852841B (en) * | 2013-06-03 | 2019-06-18 | 飞比特公司 | Heart rate data is collected |
| CN104161505A (en) * | 2014-08-13 | 2014-11-26 | 北京邮电大学 | Motion noise interference eliminating method suitable for wearable heart rate monitoring device |
| CN106551686B (en) * | 2015-09-29 | 2019-05-07 | 冯文强 | A kind of Dynamic Heart Rate measurement method, device and smartwatch |
| JP6813024B2 (en) * | 2016-05-20 | 2021-01-13 | ソニー株式会社 | Biometric information processing equipment, biometric information processing methods, and information processing equipment |
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